The present invention relates to a terminal connection structure of an electromagnetic coupling device used as an electromagnetic clutch for transmitting a rotational torque or an electromagnetic brake for braking a rotational torque.
Generally, in a friction electromagnetic coupling device such as an electromagnetic clutch, a magnetic flux generated by exciting an electromagnetic coil is flowed between a rotor and an armature arranged such that their friction surfaces oppose each other, and the friction surfaces are brought into contact with or separated from each other by a magnetic attraction force of the magnetic flux and a spring force against the magnetic attraction force, thereby transmitting or interrupting a rotational torque.
Of the electromagnetic coupling devices of this type, an electromagnetic clutch mounted on, e.g., an automobile refrigerant compressor has a predetermined lead wire length corresponding to the type of an automobile. Therefore, a certain type of a yoke incorporating an electromagnetic coil cannot be used in various types of automobiles to result in poor economy in design or inventory control. For this reason, there is a proposal of changing the design of a conventional structure, in which a winding of an electromagnetic coil and a lead wire are connected in a yoke, such that the winding of an electromagnetic coil and the lead wire are connected outside the yoke, as disclosed in, e.g., Japanese Patent Laid-Open No. 63-12108.
In this electromagnetic clutch, a pair of support metal members are formed integrally with one side wall of a coil bobbin and inserted together with a metal member support portion of the coil bobbin into a through hole of the yoke to project outside the yoke. The start and terminal end portions of a winding of an electromagnetic coil wound on the coil bobbin are extracted from extraction holes of the coil bobbin and fitted in guide grooves of the support metal members. Therefore, the start and terminal end portions of the winding of the electromagnetic coil are fixed to be aligned in the radial direction.
A pair of mount metal members mounted on a fixing member and fixing a lead wire have projecting portions inserted in a pair of metal member holding grooves formed in the support metal members. The start and terminal end portions of the winding of the electromagnetic coil aligned in the axial direction by the support metal members are inserted in caulking portions of the mount metal members and caulked therein. A fitting groove of the fixing member is fitted on a locking piece of a mount plate of the yoke. The caulking portions of the mount metal members in which the start and terminal end portions of the winding of the electromagnetic coil are inserted are caulked. The caulked portions are welded by fusing the electromagnetic coil as an enameled wire, and the welded portions have a cover fixed on the yoke by an adhesive.
However, in the above connection structure of a winding of an electromagnetic coil and a lead wire which are formed in the conventional electromagnetic clutch, the start and terminal end portions of the winding of the electromagnetic coil are extracted outside a coil bobbin and aligned in the radial direction to axially project, and these projecting end portions are covered and caulked with the caulking portions of the mount metal members, resulting in poor workability. In addition, in such caulking, the start and terminal end portions of the winding of the electromagnetic coil may be loosened in the caulking portions of the mount metal members due to poor caulking. Therefore, in order to eliminate this drawback, so-called soldering for fusing and fixing the coil end portions must be performed to pose a problem in productivity.
Furthermore, since a surge voltage absorbing member is exposed outside the structure, the member must be covered with an insulating tube such as a heat-shrinkable tube, resulting in high manufacturing cost.